CSSLint
Automated linting of cascading stylesheets
...The rules are all pluggable, so you can easily write your own or omit ones you don't want. You can integrate CSSLint into your favorite IDE to make checking your CSS code quality easy. In fact, some IDEs already have CSSLint built-in. Once you're familiar with the CSSLint command-line interface, the next step is to integrate it into your build system.